The present invention relates to a tachometric generator, particularly for measuring the speed of displacement of a movable vehicle.
Tachometric generators are known in which a shaft is connected to a drive take-off from the vehicle, and drives an element of ferro-magnetic material electromagnetically coupled to a sensor which detects its speed of rotation and generates electrical signals which when suitably processed by electronic circuits, are sent to indicator instruments disposed on the vehicle dashboard.
Known tachometric generators of the type briefly described have various disadvantages.
Vehicles are normally provided with a tachometer and an odometer; such instruments can be both of electric type, but more frequently the odometer is mechanical. Since tachometric generators do not normally include a mechanical output which can be connected, for example, by means of a flexible cable, to an input of the odometer, there is therefore required a further drive take-off and associated transmission separate from that of the tachometric generator.
Moreover, known tachometric generators include a shaft which is generally connected to the drive take-off by means of an intermediate spindle to which it is coupled prismatically. The prismatic coupling is formed with a large clearance between the parts of which it is composed in order to allow a slight relative oscillation between these shafts which compensates during operation for any possible axial misalignments or geometric errors. This results in a relative lack of precision in the transmission, with rapid wear, a risk of jamming or, in any case, with an incorrect kinematic functioning.